JP2008268172A - Image forming apparatus for forming an image on a recording medium - Google Patents

Abstract

The present invention provides a recording medium determination apparatus that can determine more types of recording mediums with high accuracy and an image forming apparatus that includes the recording medium determination apparatus and forms an image on the recording medium.
Laser light 17 is irradiated toward the surface of a recording medium 16, and the reflected light 18 is detected by a line sensor 14 as a light receiving element to detect a light receiving position and light receiving intensity, and the distribution of the light receiving position and the light receiving intensity is detected. A recording medium determination device 1 that determines the type of the recording medium 16 by comparing the state with a predetermined distribution state is provided on the upstream side of the recording medium conveyance path 653 from the fixing unit.
[Selection] Figure 1

Description

  The present invention provides an image for forming an image on a recording medium, which includes a recording medium determination device that irradiates a recording medium with laser light, detects the reflected light, and determines the type of the recording medium from the distribution state of the reflected light. The present invention relates to a forming apparatus.

  In order to form a high-quality image in an image forming apparatus such as a copying machine or a printer, it is necessary to adjust the printing method in accordance with the type of recording medium such as paper on which an image is formed. For example, good quality images cannot be obtained unless the printing method is adjusted between printing on plain paper and printing on an OHP sheet.

  In the early models, the operator manually selected the type of recording medium. However, the selection of the type of the recording medium has been promoted because there is a possibility that the selection is wrong.

  In the prior art, an apparatus for irradiating a recording medium with light and detecting reflected light and transmitted light has been proposed (for example, Patent Document 1).

In this case, the amount of transmitted light is detected by the first light receiving element disposed at a position facing the first light emitting light source with the recording medium sandwiched between the light from the first light emitting light source and the second light emission. The amount of reflected light is detected by a second light receiving element disposed on the same side as the second light emitting light source with respect to the recording medium, and the received light amount is compared with a threshold value and recorded. The type of the medium is determined.
Japanese Patent Laid-Open No. 2004-50815

  However, as will be described later, in the technique described in Patent Document 1, since the image reading apparatus outputs only the maximum value, minimum value, and average value of the observed values, the types of recording media that can be determined from the pattern of the reflected light that can be detected are limited. There was a problem of being.

  The present invention has been made in view of the above-described problems, and includes a recording medium determination apparatus that can determine more types of recording media with high accuracy, and the recording medium determination apparatus. An object of the present invention is to provide an image forming apparatus that forms an image on a medium.

  In order to achieve this object, the present invention provides a laser light source that irradiates laser light toward the surface of a recording medium, and a light receiving device that receives the reflected light of the laser light from the recording medium and outputs an output signal converted into an electrical signal. From the element and the output signal, the light receiving element detects the light receiving position of the light receiving element that receives the reflected light and the light receiving intensity of the received reflected light, and the light receiving position and the distribution state of the light receiving intensity are determined as a predetermined distribution state. There is provided a recording medium determination apparatus including a signal processing apparatus that determines a type of a recording medium by comparing.

  Furthermore, the present invention provides a recording medium supply mechanism that supplies recording media one by one, a recording medium conveyance path that conveys the recording medium supplied by the recording medium supply mechanism to a recording medium discharge section, and a recording medium in the recording medium conveyance path An image forming unit that is disposed upstream of the discharge unit and that prints an image based on image data on a recording medium conveyed by a recording medium conveying path; a fixing unit that fixes a developer on the recording medium at a predetermined temperature; and fixing Is provided on the upstream side of the recording medium conveyance path, and the recording medium determination device for detecting the type of the recording medium, and the conditions for forming an image are changed according to the type of the recording medium determined by the recording medium determination device. And a control unit for causing the recording medium determination device to receive a laser light source that irradiates a laser beam toward the surface of the recording medium, and a reflected light of the laser beam from the recording medium, and an electric signal The light receiving element that outputs the converted output signal, and the light receiving position of the light receiving element where the light receiving element receives the reflected light and the light receiving intensity of the received reflected light are detected from the output signal, and the distribution of the light receiving position and the light receiving intensity is determined. An image forming apparatus for forming an image on a recording medium, comprising: a signal processing device that determines a type of the recording medium by comparing with a predetermined distribution state.

  According to the present invention, the recording medium determination device irradiates the surface of the recording medium with laser light, and the reflected light detects the light receiving position and the light receiving intensity by the light receiving element, and the distribution state of the light receiving position and the light receiving intensity. The type of the recording medium is determined by comparing with a predetermined distribution state. For this reason, there is an effect that more types of recording media can be determined with high accuracy.

  Hereinafter, an embodiment of an image forming apparatus for forming an image on a recording medium according to the present invention will be described in detail with reference to the drawings.

<Recording medium determination device>
First, the recording medium determination apparatus will be described.

  FIG. 1 is a configuration diagram illustrating an outline of a recording medium determination apparatus according to the present embodiment. The recording medium determination apparatus 1 of this embodiment includes a laser light source 13 that irradiates a laser beam 17 toward the surface of the recording medium 16, and a laser light source that supplies power to the laser light source 13 and controls the irradiation of the laser beam 17. The drive device 11, the line sensor 14, which is a light receiving element that receives the reflected light 18 of the laser light 17 reflected by the recording medium 16 and outputs an output signal that is converted into an electrical signal, and this output signal are input and predetermined determination is performed. And a signal processing device 12 that performs processing to determine the type of the recording medium 16.

  In the present embodiment, a line sensor is used as an example of the light receiving element. In addition to the line sensor, the light receiving element in the recording medium determination apparatus of the present embodiment is an area sensor in which optical sensors are arranged in a matrix, or a pinpoint sensor in which a plurality of optical sensors are arranged at intervals. May be.

  The laser light source 13 is a device that irradiates a laser beam 17, and the type of the laser beam and the principle of laser beam oscillation are not questioned. The wavelength of the laser light 17 may be any wavelength that can be detected by the line sensor 14 described later, but visible light is desirable in terms of ease of handling. The intensity of the laser beam 17 can be arbitrarily set within a range in which the laser beam 17 is reflected by the recording medium 16 and reaches the line sensor 14 with an intensity detectable by the line sensor 14.

  FIG. 2 is a diagram illustrating a configuration example of the signal processing device 12. The signal processing device 12 receives an output signal from the line sensor 14 and converts the analog data into digital data. The A / D converter 12A performs predetermined processing on the output signal converted into the digital data, and performs a predetermined process on the recording medium 16. And a determination device 12B that outputs the type.

  The determination device 12B can be configured as follows, for example. The determination device 12B includes a processor such as a digital signal processor, a memory that stores data and programs, and a communication device that outputs data to an external device. This processor reads the program describing the processing procedure for determining the recording medium 16 from the memory and executes it, thereby processing the input output signal and outputting the determination result.

  FIG. 3 is a diagram showing the appearance of the line sensor 14. The line sensor 14 includes, for example, a linear sensor 14A that receives light and converts it into an electrical signal, and a conversion device that amplifies and converts the electrical signal converted by the sensor 14A into a state suitable for output.

  As the sensor 14A, a plurality of optical sensors arranged in a straight line may be used, or one vertically long optical sensor may be used. When a plurality of photosensors are used, the photosensors may be arranged in a line, alternately arranged, or arranged in two or more lines.

  When the recording medium determination apparatus 1 of the present embodiment is installed in an image forming apparatus that exclusively prints a small size recording medium 16, it is necessary to use a line sensor 14 having a smaller size. When the printer is installed in an image forming apparatus that prints on a large-sized recording medium, it is necessary to use a larger-sized line sensor 14. As described above, the width W in the longitudinal direction of the sensor 14A can be appropriately selected depending on the size of the recording medium 16 to be determined.

  From such a background, the length in the longitudinal direction of the sensor 14A included in the line sensor 14 is preferably 5 mm or more, and is preferably not more than the length in the longitudinal direction of the maximum recording medium to be determined.

  FIG. 4 is a diagram showing the positional relationship among the laser light source 13, the line sensor 14, and the recording medium 16. The laser light source 13 and the line sensor 14 are arranged on the same side with respect to the recording medium 16. The line sensor 14 is disposed at a position where the reflected light 18 of the recording medium 16 of the laser light 17 emitted from the laser light source 13 enters the sensor 14A.

  When the recording medium 16 totally reflects the laser light 17, the laser light source 13 and the line sensor 14 are provided for the laser light 17 emitted from the laser light source 13 and the reflected light 18 reflected by the recording medium 16. It is desirable to arrange so that the longitudinal axis of the sensor 14A included in the line sensor 14 is positioned on the plane to which the optical path belongs. Here, the longitudinal axis of the sensor 14A refers to the longitudinal center line of the light receiving surface of the sensor 14A, as indicated by 14B in FIG. When the recording medium 16 is irradiated with the laser beam 17, the spread of the reflected light 18 on the measurement surface has the maximum spread at a position intersecting the plane that the optical path of the laser beam 17 can take. Therefore, by making this coincide with the longitudinal axis of the sensor 14, the reflected light 18 can be detected in a wider range.

  The plane to which the optical path belongs is preferably substantially perpendicular to the conveyance direction of the recording medium 16 indicated by arrow A.

  Next, the detection result of the reflected light 18 in the line sensor 14 will be described. FIG. 5 is a diagram showing a detection result when the recording medium 16 is recycled paper. FIG. 5B is a graph plotting the detection results with the vertical axis representing the intensity of the detected reflected light 18 and the horizontal axis representing the light receiving position of the sensor 14A of the line sensor 14 where the line sensor 14 received the reflected light 18. is there.

  FIG. 5A shows the above detection results for each light receiving position in the sensor 14A, when the threshold value is exceeded, white (“1” when expressed as a numerical value), and black when equal to or lower than the threshold value (when expressed as a numerical value). “0”). Note that the expression of two values based on a threshold value is referred to as binarization.

  Here, the state indicated by the intensity of the reflected light 18 detected at each light receiving position in the sensor 14A of the line sensor 14 that has received the reflected light 18 is referred to as a distribution state.

  As described above, when the recording medium 16 is not glossy and rough like the recycled paper, the distribution state is low in the intensity of the reflected light 18 as a whole, and the reflected light 18 extends over a wide range of the sensor 14A. Detected.

  FIG. 6 is a view showing the detection result when the recording medium 16 is plain paper, as in FIG. Thus, when the recording medium 16 has no gloss on the surface but little roughness, the distribution state is that the intensity of the reflected light 18 is slightly stronger as a whole, and the reflected light 18 is concentrated on a part of the sensor 14A. Detected.

  FIG. 7 is a view showing the detection result when the recording medium 16 is glossy paper, as in FIG. In this way, when the recording medium 16 has a glossy surface and no roughness, the distribution state is that the intensity of the reflected light 18 is very strong as a whole, and the reflected light 18 is concentrated on the central portion of the sensor 14A. And is widely detected.

  As described above, according to the present embodiment, the distribution state differs depending on the type of the recording medium 16, and therefore the type of the recording medium 16 is determined by comparing the distribution state with a predetermined distribution state. judge.

  In addition to simply irradiating light in a spot manner, if the irradiating light is a highly coherent laser beam, changes in speckle caused by light interference due to irregular reflection on the paper surface, etc. It can be expected to be a discriminating material of this kind. For example, if the paper has a glossy surface, as shown in FIG. 7, the specularly reflected light on the surface of the paper is mainly used, so that strong light is distributed at the center. If the paper has a rough surface, the paper surface As a result, diffused light is distributed mainly over a wide range as shown in FIG. 5 and FIG.

  Next, a specific determination method will be described. The determination method is not limited, and a known method or a newly devised method can be appropriately selected. In the following, a method of comparing the Euclidean distance (first application example), a method of comparing the difference between detection values (second application example), irradiating the laser beam 17 for a certain period of time when the recording medium 16 is conveyed, A method of integrating the detection values (third application example) and a method of similarly calculating and comparing the detection values for each detection position (fourth application example) will be described.

(First application example)
The signal processing device 12 first represents the detected value, that is, the distribution state by a vector. Each element may be a relative value of the detection value, a binary numerical value of 0, 1 or observation data which is a continuous value. The column represents the position on the sensor 14A.

When there are eight detection positions and a binarized value is used, an example of a detection value vector X is
X1 = (0,1,0,0,1,1,0,0)
X2 = (0,0,1,1,1,1,1,0)
It becomes.

Here, an example of a reference vector, that is, a predetermined distribution state, is
S1 = (0, 1, 0, 0, 1, 0, 0, 0): recycled paper S2 = (0, 1, 1, 1, 1, 1, 1, 0): glossy paper. This value is stored in the memory of the signal processing device 12 as a part of a table or program.

Next, two points a (a1, a2,..., An)
b (b1, b2,..., bn)
The Euclidean distance D (a, b) is defined as shown below.

  Next, the signal processing device 12 sequentially obtains the vector of the detected value and the Euclidean distance D (a, b) of the reference vector. The result is as follows.

D (X1, S1) = 1
D (X1, S2) = 3
D (X2, S1) = 5
D (X2, S2) = 1
Further, the signal processing device 12 determines the relationship between the calculated Euclidean distance D and the threshold value. When the threshold value is 2, X1 can be determined to be close to the distribution of the state of S1 because the Euclidean distance D with S1 is equal to or less than the threshold value and the Euclidean distance D with S2 is equal to or greater than the threshold value. In this way, the signal processing device 12 determines that X1 is recycled paper. Similarly, it can be determined that X2 is close to the distribution of the state of S2, and the signal processing device 12 determines that X2 is glossy paper.

  According to the above example, it is possible to determine the recording medium 16 by using the raw data or the relative value of the detection value or by increasing the number of columns.

(Second application example)
The signal processing device 12 first represents the detected value, that is, the distribution state by a vector. Each element may be a relative value of the detection value, a binary numerical value of 0, 1 or observation data which is a continuous value. The column represents the position on the sensor 14A.

When there are 8 detection positions and a binarized value is used, an example of the detection value vector Xk is
X1 = (0,1,0,0,1,1,0,0)
X2 = (0,0,1,1,1,1,1,0)
It becomes.

Here, an example of a reference vector, that is, a predetermined distribution state, is
S1 = (0, 1, 0, 0, 1, 0, 0, 0): recycled paper S2 = (0, 1, 1, 1, 1, 1, 1, 0): glossy paper. This value is stored in the memory of the signal processing device 12 as a part of a table or program.

Next, two points a (a1, a2,..., An)
b (b1, b2,..., bn)
The difference H (a, b) is defined as follows.

  Next, the signal processing device 12 sequentially obtains a difference H (a, b) between the detected value vector and the reference vector. The result is as follows.

H (X1, S1) = + 1
H (X1, S2) =-2
H (X2, S1) = + 3
H (X2, S2) =-1
Furthermore, the signal processing device 12 determines the relationship between the calculated difference H and the threshold range. When the threshold range R is set to −1 ≦ R ≦ + 1, the difference H from S1 is within the threshold range, and the difference H from S2 is outside the threshold range. Can be judged. In this way, the signal processing device 12 determines that X1 is recycled paper. Similarly, it can be determined that X2 is close to the distribution of the state of S2, and the signal processing device 12 determines that X2 is glossy paper.

  According to the above example, it is possible to determine the recording medium 16 by using the raw data or the relative value of the detection value or by increasing the number of columns.

(Third application example)
When the recording medium 16 is moving, the laser light source 13 irradiates the recording medium 16 with a laser beam 17 for a certain period of time. At this time, the line sensor 14 receives the reflected light 18 of the laser beam 17 from the recording medium 16 for a certain time, and outputs an output signal converted into an electric signal to the signal processing device 12.

  The signal processing device 12 first represents the detected value, that is, the distribution state by a vector. Each element may be a relative value of the detection value, a binary numerical value of 0, 1 or observation data which is a continuous value. The column represents the position on the sensor 14A.

When there are 8 detection positions and a binarized value is used, an example of a detection value vector Xt detected at time t is
X1 = (0,1,0,1,1,1,1,0)
X2 = (0,0,1,1,1,1,1,0)
X3 = (0,1,0,1,1,1,1,0)
It becomes.

Next, when the detection is performed i times during the above-mentioned fixed time, the detection value a1 (a11, a21,..., An1)
a2 (a12, a22, ..., an2)
:
ai (a1i, a2i, ..., ani)
The integral value I is defined as follows. That is, the detection value is added for each detection position to calculate a vector.

  Next, the signal processing device 12 sequentially obtains the integral value I of the vector of detected values. An example of the result is as follows.

I = (0,2,1,3,3,3,3,0)
The integral value I is compared with a reference vector according to the procedure shown in the first application example or the second application example, and the type of the recording medium 16 is determined.

  According to the above example, it is possible to determine the recording medium 16 by using the raw data or the relative value of the detection value or by increasing the number of columns.

(Fourth application example)
When the recording medium 16 is moving, the laser light source 13 irradiates the recording medium 16 with a laser beam 17 for a certain period of time. At this time, the line sensor 14 receives the reflected light 18 of the laser beam 17 from the recording medium 16 for a certain time, and outputs an output signal converted into an electric signal to the signal processing device 12.

  The signal processing device 12 first represents the detected value, that is, the distribution state by a vector. Each element may be a relative value of the detection value, a binary numerical value of 0, 1 or observation data which is a continuous value. The column represents the position on the sensor 14A.

When there are 8 detection positions and a binarized value is used, an example of a detection value vector Xt detected at time t is
X1 = (0,1,0,1,1,1,1,0)
X2 = (0,0,1,1,1,1,1,0)
X3 = (0,1,0,1,1,1,1,0)
It becomes.

Next, when the detection is performed i times during the above-mentioned fixed time, the detection value a1 (a11, a21,..., An1)
a2 (a12, a22, ..., an2)
:
ai (a1i, a2i, ..., ani)
The average value B is defined as shown below. That is, the detection value is added for each detection position, and further divided by the number of detections to obtain an average value of the detection values for each detection position, thereby calculating a vector.

  Next, the signal processing device 12 sequentially obtains the average value B of the detected value vectors. An example of the result is as follows.

B = (0, 0.66, 0.33, 1, 1, 1, 1, 0)
If this is further rounded to a value less than 1 to 0, the result is as follows.

Br = (0,0,0,1,1,1,1,0)
The average value Br is compared with a reference vector according to the procedure shown in the first application example or the second application example, and the type of the recording medium 16 is determined.

  According to the above example, it is possible to determine the recording medium 16 by using the raw data or the relative value of the detection value or by increasing the number of columns.

  In addition, for example, a method of calculating the number of pixels exceeding a certain threshold value of the sensor instead of looking at the distribution of light appearing on the line sensor and determining the type of paper from the number of pixels, or making the threshold variable. By doing so, a method of discriminating the type of paper from the correlation between the threshold and the number of pixels can be adopted. In other words, the type of paper is quantified and discriminated based on how many points having brightness above a certain threshold are seen. By doing so, distribution pattern matching is not required, and high-speed detection is possible.

  In the present embodiment, it is desirable to use the line sensor 14 as the light receiving element. The reason will be described below. FIG. 8 is a diagram comparing ranges in which the reflected light 18 can be detected.

  FIG. 8C is a side view of a state in which the recording medium 16 is irradiated with the laser light 17 and the reflected light 18 is generated. A dotted line 80 indicates the range in which the reflected light 18 can be detected by the range of scattering of the reflected light 18 and the photodetector such as the line sensor 14 or the area sensor.

  FIG. 8A shows a range 81 of the reflected light 18 that can be detected by the area sensor. FIG. 8B is a diagram showing a range 82 of the reflected light 18 that can be detected by the sensor 14 </ b> A of the line sensor 14. As shown in FIG. 3, W is the length of the sensor 14A of the line sensor 14 in the longitudinal direction.

  The closer to the circumference of the dotted line 80, the more sensitive the presence and intensity of the reflected light 18 and the state of the surface of the recording medium 16. This is also shown in the diagrams shown in FIGS. Therefore, in an apparatus that determines the type of the recording medium 16 by detecting the reflected light 18, it can be said that the determination accuracy is higher when the reflected light 18 is detected in a wider range.

  Here, when FIG. 8A is compared with FIG. 8B, the line sensor 14 is detected from the detectable range 81 of the reflected light 18 when the area sensor is used, that is, the range indicated by the one-dot broken line 83. It can be seen that the range 82 in which the reflected light 18 can be detected, that is, the range indicated by the one-dot broken line 84 is wide, and the vicinity of the dotted line 80 can be detected.

  Therefore, the detection accuracy of the recording medium is higher when the line sensor is used than when the area sensor is used. Here, it is conceivable to use an area sensor that can detect the same range as the line sensor described above, but in this case, the size of the area sensor becomes very large and cannot be installed in, for example, an image forming apparatus. Problems arise. However, the line sensor requires a small space for installation and can be installed in the image forming apparatus.

  The recording medium determination apparatus 1 of this embodiment can be installed in an image forming apparatus. When installed in the image forming apparatus, it can be configured as follows, for example. The recording medium determining apparatus 1 is preferably installed at a position where the recording medium 16 can be irradiated with the laser light 17 from the laser light source 13 and the light incident on the line sensor 14 other than the light from the laser light source 13 is small. The determination result of the recording medium by the recording medium determination device 1 is output to the control unit of the image forming apparatus, and the control unit of the image forming apparatus adjusts the printing method according to the determination result. The control unit of the image forming apparatus is configured to control the operation of the recording medium determination apparatus 1.

  As described above, in the present embodiment, the recording medium determination apparatus 1 irradiates the laser beam 17 toward the surface of the recording medium 16 and detects the light reception position and light reception intensity of the reflected light 18 by the line sensor 14. The type of the recording medium 16 is determined by comparing the distribution state of the light receiving position and the light reception intensity with a predetermined distribution state. For this reason, the range in which the reflected light 18 can be detected is expanded, and it is possible to determine more types of the recording medium 16 with high accuracy.

<Image forming apparatus>
Next, the image forming apparatus will be described.

  FIG. 9 is a diagram illustrating a configuration example of the image forming apparatus. As shown in FIG. 9, a document table 602 for placing a document, which is formed of a transparent material such as a glass plate, is provided on the upper part of the apparatus main body 601. Further, a cover 603 is installed on the apparatus main body 601 so as to be openable and closable so as to cover the document table 602.

  A scanning unit (not shown) that optically reads an image of a document placed on the document table 602 is provided on the lower surface side of the document table 602 inside the apparatus main body 601. For example, the scan unit includes a carriage 604, reflection mirrors 606, 607, and 608 that reflect light from an exposure lamp 605 reflected on a document, a zooming lens block 609 that scales the reflected light, and a CCD ( Charge Coupled Device) 610. The carriage 604 includes an exposure lamp 605 that emits light toward the document table 602, and is configured to reciprocate along the lower surface of the document table 602.

  The carriage 604 moves forward while turning on the exposure lamp 605 to expose a document placed on the document table 602. The reflected light image of the document placed on the document table 602 by this exposure is projected onto the CCD 610 via the reflection mirrors 606, 607, and 608 and the zoom lens block 609. The CCD 610 outputs an image signal corresponding to the reflected light image of the projected document.

  An image forming unit 220 is provided below the scan unit in the apparatus main body 601. The image forming unit 220 includes, for example, a print engine (not shown) and a process unit (not shown).

  The print engine includes an exposure unit 611. The process unit has an endless shape arranged to face the exposure unit 611 across the photosensitive drums 621, 622, 623, and 624, and the photosensitive drums 621, 622, 623, and 624 arranged along the exposure unit 611. Transfer belt 625, a drive roller 626 for driving the transfer belt 625, and primary transfer rollers 641, 642, 643 arranged to face the photosensitive drums 621, 622, 623, 624 with the transfer belt 625 interposed therebetween. 644 and a transfer roller driving unit for driving the primary transfer rollers 641, 642, 643, and 644.

  The transfer belt 625 is stretched around a drive roller 626, guide rollers 627, 628, 629, and a driven roller 630, and receives the power from the drive roller 626 to rotate counterclockwise. The guide roller 627 is provided so as to be movable up and down, and moves toward the transfer belt 625 in response to the rotation of the cam 631. As a result, the guide roller 627 displaces the transfer belt 625 toward the photosensitive drums 621, 622, 623, 624.

  The image forming unit 220 forms an image based on the image data (image signal output from the CCD 610), and prints the image on a recording medium that is being conveyed. That is, the image signal output from the CCD 610 is appropriately processed and then supplied to the exposure unit 611. The exposure unit 611 applies the laser beam B1 corresponding to the yellow color image signal to the yellow color photosensitive drum 621, the laser beam B2 corresponding to the magenta color image signal to the magenta color photosensitive drum 622, and the cyan color. The laser beam B3 corresponding to the image signal is emitted toward the cyan color photosensitive drum 623, and the laser beam B4 corresponding to the black color image signal is emitted toward the black color photosensitive drum 624.

  The primary transfer rollers 641, 642, 643, 644 are moved (lowered) toward the transfer belt 625, thereby bringing the transfer belt 625 into contact with the photosensitive drums 621, 622, 623, 624, and the photosensitive drum. The visible images on 621, 622, 623 and 624 are transferred to the transfer belt 625.

  Around the photosensitive drum 621, a drum cleaner, a charge eliminating lamp, a charging unit, and a developing unit (not shown) are sequentially arranged. The drum cleaner has a drum cleaning blade in contact with the surface of the photosensitive drum 621, and the developer remaining on the surface of the photosensitive drum 621 is scraped off by the drum cleaning blade.

  The static elimination lamp removes the electric charge remaining on the surface of the photosensitive drum 621. The charging unit applies a high voltage to the photosensitive drum 621 to charge the surface of the photosensitive drum 621 with an electrostatic charge. The surface of the photosensitive drum 621 that has been charged is irradiated with a laser beam B1 emitted from the exposure unit 611. By this irradiation, an electrostatic latent image is formed on the surface of the photosensitive drum 621. The developing unit supplies a yellow color developer (toner) to the surface of the photosensitive drum 621 to visualize the electrostatic latent image on the surface of the photosensitive drum 621.

  Similarly, the other photosensitive drums 622, 623, and 624 visualize the electrostatic latent images on the surfaces of the photosensitive drums 622, 623, and 624 by using developing materials of corresponding colors.

  A cleaner 636 is provided at a position facing the drive roller 626 of the image forming unit 220 with the transfer belt 625 interposed therebetween. The cleaner 636 has a cleaning blade 636a that contacts the transfer belt 625, and the developer remaining on the transfer belt 625 is scraped off by the cleaning blade 636a.

  The print mode is changed as follows. In the vicinity of the primary transfer rollers 641, 642, 643, 644, hooks 671, 672, 673, 674 are provided. The hooks 671, 672, 673, 674 engage with the shafts of the primary transfer rollers 641, 642, 643, 644 while rotating and lift the shafts to move the primary transfer rollers 641, 642, 643, 644. The photosensitive drums 621, 622, 623, and 624 are moved away from each other. Either the primary transfer rollers 641, 642, 643, 644 are not moved, or the printing mode such as the full color mode, the all separation mode, and the monochrome mode is changed by changing the combination of the moving ones.

  Next, a storage mechanism and a supply mechanism for the recording medium will be described. Below the exposure unit 611, a plurality of recording medium cassettes 650 for storing recording media are provided. These recording medium cassettes 650 contain a large number of recording media P of different recording medium types in a stacked state. A recording medium supply mechanism 221 for supplying the recording medium in the recording medium cassette 650 one by one from the top is provided at the exit portion (right side in the drawing) of the recording medium cassette 650. Then, the recording medium supply mechanism 221 takes out the recording medium P one by one from any one recording medium cassette 650. This take-out recording medium supply mechanism 221 includes a pickup roller 651, a recording medium supply roller 652a, and a separation roller 652b, and separates the recording medium P taken out from the recording medium cassette 650 one by one and conveys the recording medium. Supply to path 653.

  Next, the conveyance path of the recording medium will be described. The recording medium conveyance path 653 extends to the upper recording medium discharge port 654 via the driven roller 630 of the image forming unit 220. The recording medium discharge port 654 faces a recording medium discharge portion 655 that is continuous with the outer peripheral surface of the apparatus main body 601. Further, on the start end side of the conveyance path 653, conveyance rollers 656 are provided in the vicinity of the respective recording medium supply mechanisms 221. The recording medium conveyance path 653 conveys the supplied recording medium to the recording medium discharge unit 655 when the recording medium is supplied by any recording medium supply mechanism 221.

  A secondary transfer roller 657 is provided at a position facing the driven roller 630 in the middle of the recording medium conveyance path 653 with the transfer belt 625 interposed therebetween. A registration roller 658 is provided at a position before the driven roller 630 and the secondary transfer roller 657 in the conveying direction.

  The registration roller 658 moves the recording medium P at a timing synchronized with a transfer operation, which is an operation of transferring an image formed of the developer (toner) to the recording medium by the transfer belt 625 and the secondary transfer roller 657. The sheet is fed between the transfer belt 625 and the secondary transfer roller 657. The secondary transfer roller 657 is a visible image formed by a developer (toner) transferred to the transfer belt 625 while sandwiching the recording medium P fed from the registration roller 658 with the transfer belt 625 on the driven roller 630. Is transferred to the recording medium P and printed. As described above, the registration roller 658 conveys the recording medium P to the image forming unit 220 including the transfer belt 625 and the secondary transfer roller 657 in synchronization with the transfer operation of the image forming unit 220.

  A heat roller 659 for heat fixing and a pressure roller 660 in contact with the heat roller 659 are provided at a position downstream of the secondary transfer roller 657 in the recording medium conveyance path 653. The image transferred to the recording medium P is fixed by the heat roller 659 and the pressure roller 660. A recording medium discharge roller 661 is provided at the end of the recording medium conveyance path 653.

  The apparatus main body 601 may be provided with an automatic duplex unit (hereinafter referred to as ADU) 222. The ADU 222 is installed so as to connect the sub-transport path 662 that is a path for transporting the recording medium P in the ADU 222 to the end of the recording medium transport path 653 and the entrance to the registration roller 658. The sub conveyance path 662 branches from the downstream side of the recording medium conveyance path 653 with respect to the image forming unit 220 (the end of the recording medium conveyance path 653), and the upstream side of the recording medium conveyance path 653 with respect to the image forming unit 220 (of the registration roller 658). (Upstream position)

  The sub transport path 662 reverses the front and back of the recording medium P for double-sided printing. Recording medium supply rollers 663, 664, 665 are provided in the sub-conveying path 662, and the ADU 222 reversely feeds the recording medium P conveyed from the image forming unit 220 to the recording medium discharging unit 655, and passes through the sub-conveying path 662. The sheet is conveyed and merged with the recording medium conveyance path 653 on the upstream side of the image forming unit 220. When transported in this way, the front and back of the recording medium P are reversed.

  The recording medium P returned to the upstream side of the image forming unit 220 by the sub-conveying path 662 joins the recording medium conveying path 653 and then synchronizes with the transfer operation of the image forming unit 220 by the registration roller 658 to transfer the recording belt. 625 and the secondary transfer roller 657 are sent to a transfer position where they contact. In this way, the visible image on the transfer belt 625 is also transferred to the back surface of the recording medium P and printed.

  When the double-sided printing is designated by the operation panel 724 provided in the apparatus main body 601 or a computer connected to the apparatus main body 601 via the network, the sub-transport path 662 of the ADU 222 is the front and back of the recording medium P described above. It will be in the state which performs the operation | movement which reverses.

  Next, an additionally provided device will be described. In the example of the apparatus main body 601 shown in FIG. 9, two recording medium cassettes 650 are provided as recording medium supply sources. Three or more recording medium cassettes 650 may be provided in the apparatus main body 601. In addition, although not shown, a large-capacity recording medium feeder (hereinafter referred to as SFB) or a large capacity recording medium feeder (hereinafter referred to as SFB) which is a recording medium supply mechanism capable of stacking and storing thousands of recording media. , Referred to as LCF). These SFB and LCF are installed in the apparatus main body 601 so that the path for supplying the recording medium merges with the recording medium conveyance path 653.

  Next, the installation position of the recording medium determination apparatus 1 of the present embodiment will be described. FIG. 10 is a diagram showing the vicinity of the recording medium conveyance path 653 in detail. Hereinafter, the heat roller 659 and the pressure roller 660 are collectively referred to as a fixing unit 721. The fixing unit 721 fixes the developer onto the recording medium P by conveying the recording medium P onto which the developer (toner) has been transferred by the heat roller 659 while the pressure roller 660 applies pressure.

  The apparatus main body 601 is provided with a control unit (not shown). This control unit can be configured using, for example, a CPU, a memory such as a ROM or a RAM, an LSI, or the like. The control unit controls the temperature of the heat roller 659. For example, when there is no signal from the control unit, the heat roller 659 maintains a predetermined temperature according to the type of the recording medium P and waits. When a fixing start signal is received, the heat roller 659 sets the temperature according to the instruction. Change.

  Since the apparatus main body 601 has such a configuration and fixes the developer, the recording medium determination apparatus 1 is installed upstream of the fixing unit 721 in the recording medium conveyance path 653.

  When only one recording medium determination device 1 is used, it is installed at the first installation position 223 shown in FIG. The first installation position 223 is an upstream side of the recording medium conveyance path 653 with respect to the image forming unit 220 and is an upstream side of the registration roller 658. Further, when the SFB 712 or the LCF 705 is installed, the first installation position 223 is a position on the downstream side from the junction point between the recording medium supply path from the SFB 712 and the LCF 705 and the recording medium conveyance path 653. The recording medium determination device 1 is installed toward the surface of the recording medium to be conveyed.

  By disposing the recording medium determination device 1 at the first installation position 223, the recording medium P that is conveyed on the recording medium conveyance path 653 from all the recording medium supply sources by one recording medium determination device 1. The type can be detected.

  Depending on the model of the image forming apparatus, there is a case where the image forming apparatus cannot be installed at the first installation position 223 due to the arrangement of various components inside the apparatus main body 601. There is also a model in which the SFB 712 is attached as an option. In these cases, the recording medium determination apparatus 1 can be provided at the following two locations.

  This will be described with reference to FIG. The second installation position 715 is a position upstream of the image forming unit 220 of the recording medium conveyance path 653 and upstream of the registration roller 658 in the recording medium conveyance path 653, and is the recording position of the uppermost cassette device 650. The position is downstream of the medium supply roller 652 a and the separation roller 652 b and is downstream of the joining position of the recording medium supply path from the LCF 705 and the recording medium transport path 653. The recording medium determination device 1 is installed toward the surface of the recording medium to be conveyed. The recording medium determination apparatus 1 may be installed in the vicinity of the conveyance roller 656 at the second installation position 715.

  The third installation position 718 is a position upstream from the joining position of the recording medium supply path from the SFB 712 and the recording medium conveyance path 653. The recording medium determination device 1 is installed toward the surface of the recording medium to be conveyed. The recording medium determination apparatus 1 may be installed in the vicinity of the conveyance roller 717 at the third installation position 718.

  By disposing the recording medium determination apparatus 1 at the second installation position 715 and the third installation position 718, the recording medium determination apparatus 1 is installed at the installation position 718 as necessary in a model in which the SFB 712 is optionally attached. There is an effect that can be.

  Next, an application example relating to processing of a determination result signal output from the recording medium determination apparatus 1 will be described. On the upper surface of the apparatus main body 601, an operation panel 724 that is used for selecting the type of the recording medium P and for inputting information when displaying information or setting data is attached. The operation panel 724 is connected to the control unit. This control unit controls the speed of a motor that rotationally drives each roller for transporting the recording medium, and also stops and restarts the transportation of the recording medium.

  First, the control unit stores the default recording medium type or the recording medium type input from the operation panel 724 in the memory as a setting recording medium, and sets the standby temperature of the heat roller 659 according to the setting recording medium. To do.

  Next, when the recording medium P is conveyed and the recording medium determination apparatus 1 determines the type of the recording medium P, the recording medium determination apparatus 1 outputs a determination result signal to the control unit. The control unit sets, for example, the recording medium conveyance speed, the rotation speed of the fixing unit 721, and the temperature at the time of fixing the heat roller 659 according to the determination result, and transmits an instruction to these devices.

  As described above, the image forming apparatus of this application example first sets the setting recording medium, and then further sets conditions such as the speed and temperature during fixing according to the type of the recording medium determined by the recording medium determination apparatus 1. For this reason, there is an effect that it is possible to quickly carry out finer setting conditions and fixing according to the type of recording medium.

<Possibility in the embodiment of the present invention>
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a block diagram which shows the outline | summary of a recording-medium determination apparatus. It is the figure which showed the structural example of the signal processing apparatus. It is the figure which showed the external appearance of the line sensor. It is the figure which showed the positional relationship of a laser light source, a line sensor, and a recording medium. It is the figure which showed the detection result when a recording medium is a recycled paper. It is a figure showing a detection result when a recording medium is plain paper. It is a figure showing a detection result when a recording medium is glossy paper. It is the figure which compared the range which can detect reflected light. 1 is a diagram illustrating a configuration example of an image forming apparatus. FIG. 4 is a diagram illustrating in detail a vicinity of a recording medium conveyance path.

Explanation of symbols

1: recording medium determination device,
13: Laser light source,
14: Line sensor,
16: Recording medium,
223: first installation position,
601: the device body,
705: LCF,
715: Second installation position,
718: Third installation position.

Claims (6)

A laser light source that emits laser light toward the surface of the recording medium;
A light receiving element that outputs an output signal obtained by converting light reflected by the recording medium of the laser light;
From the output signal, the light receiving element detects the light receiving position of the light receiving element that has received the reflected light and the light receiving intensity of the received reflected light, and the light receiving position and the distribution state of the light receiving intensity are predetermined. A signal processing device for determining the type of the recording medium by comparing with a distribution state;
A recording medium determination apparatus comprising: When the recording medium totally reflects the laser beam,
The light receiving element is arranged so that a longitudinal axis of a sensor of the light receiving element is positioned on a plane to which an optical path of laser light irradiated from the laser light source and reflected by the recording medium belongs. The recording medium determination apparatus according to claim 1. When the recording medium is moving,
The laser light source irradiates the recording medium with the laser light for a certain period of time,
The light receiving element receives reflected light from the recording medium of the laser light for the predetermined time, and outputs an output signal converted into an electrical signal,
The signal processing apparatus includes a signal processing apparatus that determines the type of the recording medium by comparing a state of an average distribution of the received light intensity at the light receiving position for the predetermined time with a predetermined distribution state. The recording medium determination device according to claim 1, wherein When the recording medium is moving,
The laser light source irradiates the recording medium with the laser light for a certain period of time,
The light receiving element receives reflected light from the recording medium of the laser light for the predetermined time, and outputs an output signal converted into an electrical signal,
The signal processing device includes a signal processing device that determines the type of the recording medium by comparing a distribution state of the integrated value of the received light intensity at the light receiving position for the predetermined time with a predetermined distribution state. The recording medium determination apparatus according to claim 1, wherein:   2. The recording medium determination device according to claim 1, wherein a length of a sensor included in the light receiving element is 5 mm or more and is equal to or less than a length of a maximum recording medium to be determined. . A recording medium supply mechanism for supplying recording media one by one;
A recording medium conveyance path for conveying the recording medium supplied by the recording medium supply mechanism to a recording medium discharge unit;
An image forming unit disposed upstream of the recording medium discharge unit in the recording medium conveyance path and printing an image based on image data on a recording medium conveyed by the recording medium conveyance path;
A fixing unit for fixing the developer to the recording medium at a predetermined temperature;
A recording medium determination device provided on the upstream side of the recording medium conveyance path from the fixing unit and detecting the type of the recording medium;
A control unit that changes a condition when forming an image according to the type of the recording medium determined by the recording medium determination device;
The recording medium determination device is
A laser light source that emits laser light toward the surface of the recording medium;
A light receiving element that receives reflected light from the recording medium of the laser light and outputs an output signal converted into an electrical signal;
From the output signal, the light receiving element detects the light receiving position in the light receiving element that received the reflected light and the received light intensity of the reflected light received,
A signal processing device that determines the type of the recording medium by comparing the distribution state of the light receiving position and the received light intensity with a predetermined distribution state;
An image forming apparatus for forming an image on a recording medium.

Images